If I hadn't practiced when I was young,I----able to play so

选D.
考察虚拟语气
表示与过去事实相反的情况
　　从句：If 主语+had+done
　　主句：主语+should/would/could/might+have done　
　　eg：
　　1． If I had got there earlier,I should/could have met her.如果我早到那儿,我就会见到她.
　　（事实：去晚了）
　　2．If he had taken my advice,he would not have made such a mistake.如果他听我的劝告的话,就不会犯这样的错误了.
　　（事实：没有听我的话）